Apparatus for producing ground or polished glass strip



Jan. 20, 1942. e. H. BAILLIXE ETAL 2,270,244

APPARATUS FOR PRODUCING GROUND OR POLISHED GLASS STRIP Filed Feb. 20, 1939 v v I AWE/Woks W ,MMQM Wa I 'w 4 2 Sheets-Sheet l Jan. 20, 1942. BA|| |E ETAL 2,270,244

APPARATUS FOR PRODUCING GROUND OR POLISHED GLASS STRIP Filed Feb. 20, 1939 2 Sheets-Sheet 2 Patented Jan. 20, 1942 APPARATUSTOR PRODUCING GROUND R POLISHED GLASS STRIP;

Granville Hugh Baillie, London;r.and ,,:Frede -ic Barnes Waldron, Prescot, Englaniassignors to Pilkington Brothers Limited, Liverpool, Eng,- land, a limited liability company.

Application February 20, 1939, Serial No. 257,322 I In Great Britain February-22,1938

11 Claims. (c1. 511-112) This invention relates to the production of ground or polished glass strip from the molten mass in a continuousprocess and has for its object, to provide means for driving the strip throughthe apparatus.

The type of apparatus to which the invention is applicable is thatin which a continuous glass strip is formed from ,the molten mass by astripforming apparatus andis then passed through a leer and then through a grinding or grinding and polishing apparatusin which the toolsoperate simultaneously on both sidesof the strip, while thestrip is driven between the tools by a plu rality of pairs of rollers gripping the strip. I

Since the invention is equally applicable to apparatus in which the strip is groundonly and to apparatus in which it isfirst ground and then polished, the term finishing apparatuswhen usedin the following will be deemed to mean 7 grinding or grinding and polishing apparatus.

The speed of formation ofthe strip is determined primarily by the speed of the rolling mae chine .or other forming apparatus. Sometimes, however, the rollers on which the strip rests while still plastic are driven slightly faster than the, strip issuing from the forming machine so as to stretch the strip, but in any case the strip is delivered to the leer at a predetermined speed. The leer rollers are driven at this speed or groups of them are driven at speeds of which the average is this speed. The small differences in diam- I eter which necessarily exist in the rollers do not lead to any difiiculty, because the strip rests on the rollers by its weight and any roller having a diameter such that its peripheral speed differs from that of the strip is able to slip on the strip.

In the grinding apparatus, however, a considerable tractive force must be applied to the strip by the rollers in order-to overcome the frictional resistance between the strip and the tools. Sufficient force can be applied only by pairs of rollers pressed together, to grip the strip. These rollers, therefore, cannot slip to compensate for small. differences in diameter, at any rate until the tension or compression in the stripis considerably greater than the normal.

In apparatus heretofore constructed, the driving rollers in the, grinding machine'have been driven at a rate of revolution which bears a constant ratio to that of the leer rollers. Since thestrip contracts between the leer and the grinding machine because it cools, the rate of revolution of the rollers in the grinding machine has been such as to give a, peripheral speed as nearlyas possibleequalto the speed of the strip in the grindingapparatus, which is less than the above-mentionedpredetermined speed of the strip. It is, of course, impossibleto maintainthe speed of the rollers always correct. and to avoid small differences in diameter in the rollers, and the tension and compressions which result from them have in practice caused breakage ofthe strip, either by direct tensilebreak or as the result of buckling the strip.

According to the invention, the driving means for at least one roller of each pair of gripping rollers is a weight or spring exercising. a substantially constant torque on the rolleror rollers and motor driven means are employed to maintain the :weight in operative position or the spring in operative form. r

In the accompanying. drawings- Figure l is a diagrammatic plan view of part of afinished strip producing apparatus operate ing on a continuous strip;

Figure 2 is a horizontalseotion through a roller driving device;

Figure 3 is a section along the line A-Aof Figure 2;

Figure 4 isa plan View of a device for driving the device of Figure 2;

Figured is a diagrammatic view in elevation of an alternative form of driving device;

Figure 6 is a form of devicealternative to the deviceof Figure 4; and

Figure showsra means. forwusing a spring instead of a weight.

Referring to Figure 1, molten glass 12 from the tank [3 is fed to the strip forming apparatus 14, and.the formed strip I passes as acontinuous 1,

strip throughthe leer 1,5 and then between a plurality of grinding tools 2, the lower tools opcrating on the ;under side of the strip being beneath the uppertools shown. Between each pair Q of tools is a pairof rollersv 3; which grip: the strip, ,and each pairgis drivenbya weight orspring while theweight is maintained in opere atiyeqposition or the spring in operative form by t emo or ou h the comm h t-5, a d]- gearingwhich will be described with reference to o er-fi ure Referringto Figures 2 and 3, which show one 3 form of the inventiomthe shaftt of one of the rollers 3 is supported in bearings (not; shown) at 1 andcarries keyed to it the sun wheel 8. of a planetarygear. ,The outer internal toothed gear I wheel f theplanetary gear is loose on the portion ID of the shaft 6. Attached to the wheelfl is arworm-wheel, H with which a worm-l2 en-- gagee-driven -by a vertical shaft l3, The planet,

wheels [4 of the planetary gear turn on studs fixed in a drum [5 which is loose on the portion I6 of the shaft 6. A weight I! is hung on a steel tape [8 wound round the drum l5. (The drum I5 and weight ll, which do not properly appear in Figure 3, are shown therein in dotted lines.) Assuming the wheel 3 to be held stationary, the weight I1 tending to turn the drum IS with the planet wheels I4 clockwise (looking at Figure 3) would also tend to turn the sun wheel 8 and the roller 3 clockwise. If now the wheel 9 be driven counter-clockwise by means of the worm l2, it will tend to turn the drum l5 counterclockwise to raise the weight l'l. Thus, while the roller 3 is rotating, the worm I2 could be turned at a speed which will keep the weight I! stationary, or at a faster speed which will gradually raise the weight [1, or at a slower speed which will allow the weight I! to fall gradually, and in any case the torque which is applied to the roller 3 depends on the weight only (for a device of given dimensions) and is the same whether the weight is stationary or rising or falling, apart from small variations due to friction of the parts.

Since in practice it is impossible to turn all the worms l2 at a speed which will keep the weights I'l stationary, provision must be made to alter the speed of a worm when the corresponding weight, in rising or falling reaches the limit of its permissible travel.

One method of effecting this is shown in Figure 4, in which the worm shaft I3 carries a wormwheel I!) driven by a worm 20 on a shaft 2|, which carries one member 22 of a magnetic clutch, of which the other member 23 is on a shaft 24 having a bevel gear wheel 25 engaging a bevel gear wheel 26 on the common shaft 5. The motor, 4 is arranged to drive the worm shaft [3 through this gearing and magnetic clutch at a speed which is slightly higher than corresponds to the speed at which the strip is delivered to the leer, so that the weight I! gradually rises, the excess speed being sufficient to ensure that, in spite of the inevitable variations in diameter of the. rollers, no single weight falls. An arm 63 on the weight I! is adapted to throw over the lever 64 counterclockwise when the weight reaches the lower limit of its travel and, by means of the arm 65 and connection 66, to throw it over clockwise into the position shown when the weight reaches its upper limit. The lever 64 closes the switch 61 when the lever 64 is thrown over counterclockwise and opens it when the weight reaches its upper limit. The switch 6'! is connected by the line 68 to one brush 69 of the magnetic clutch 22, 23, the other brush and the other line from the switch being connected to a source of current. Thus, when the weight I'I reaches the upper limit of its travel, it opens the switch 61 and opens the circuit of the magnetic clutch 22, 23. The worm shaft 13 is then no longer driven, and the outer gear Wheel 9 of the planetary gear is held stationary. The weight I'I then continues to drive the roller 3 by falling, and, when it reaches the lower limit of its travel, it closes the switch 61 and the circuit of the magnetic clutch and the motor drive of the worm shaft l3 starts again. If, for example, the motor drives the worm shaft I3 at a speed 5% too fast, and if the weight falls from its upper to its lower limit in one minute, it will take twenty minutes to rise from the lower to the upper limit.

Figure 5 shows diagrammatically themechanicalequivalent of the planetary gear of Figures 2 and 3, using a chain and pulleys. The roller shaft 6 carries a chain wheel 21, and a chain 28 passes round it, round a pulley 29 carrying the weight 11, round a motor-driven chain wheel 33, round a pulley 3| carrying a small counterweight 32, sufficient to take up the slack of the chain, and over an idler pulley 33. The chain wheel 30 is driven by the shaft 34, through the two worm gears 35, 36. The shaft 34 which is the equivalent of the shaft 2| of the arrangement shown in Figure 4, is driven by an alternative arrangement using individual motors. The motor 31 is a direct current shunt motor having a resistance 33 in the shunt circuit, with means for short-circuiting the resistance. With the resistance shortcircuited, the motor 3! is arranged to drive the chain wheel 30 at a speed slightly too slow and with the resistance in circuit, to drive it at a speed slightly too fast, that is to say, at a speed higher than corresponds to the speed at which the strip is delivered to the leer. The two wires 39 adapted to short-circuit the resistance 38 are taken to a tipping switch 40, such as an ordinary mercury switch, located so that a projection 4| on the weight operates the switch to open the circuit of the wires 39 at its lower limit of travel. Thereby the motor 3'! is caused to run at its higher speed, so as gradually to raise the weight I1. When this reaches its upper limit, the projection 4| strikes the arm 42 and this, connected by cord 43 to the switch 40, closes it to shortcircuit the resistance 38 and cause the motor to run at its lower speed, and so allow the weight to fall again gradually.

Figure 6 shows a device whereby the bevel wheel 25 of the device shown in Figure 4 is driven at either of two speeds by the drive shaft 5, one speed being slightly above and the other slightly below the speed which would keep the weight I! stationary.

The shaft 45 carries two gear wheels 52 and 53 engaging respectively gear wheels 54 and 55, loose on the shaft 5, and attached respectively to members 56 and 51 of a double magnetic clutch, of which the central part 58 is fast. on the shaft 5. The drive shaft 5 is driven at approximately the correct speed, that is to say, the speed which would keep the weights approximately stationary, and the ratios of the gears 52, 54 and 53, 55 are such as to drive the gear wheel 25 at speeds slightly above and slightly below this speed.

Figure '7 shows how a spring 59 may be substituted for the weight I! in the device of Figures 2 and 3. The lower end of the spring is fixed at 60, while the upper end carries a pulley 6| round which the steel tape l8 from the drum [5 passes and is fixed at 62. Since the range of movement of a spring, while keeping the torque it exercises sufiiciently constant, is small, it is generally less suitable than a weight.

When the two rollers of each pair are positively driven, the above-described devices adapted to apply constant torque are preferably applied to each of the two rollers. However, when the two rollers are of different materials, for instance, of soft and hard rubber, so that the grip of one of them on the glass is substantially less than that of the other, whereby the one with less grip is able to slip without exercising undue torque, the roller with greater grip may be driven by one of the above-mentioned devices, and the other roller may be geared to it.

When a rubber roller exercises torque to drive a strip of glass, there may be creep between the roller and the glass, so that the peripheral speed of h i S h y: h r n h p edh p of t eii s in ap r t f ra lr a r v of .the glass ,If this be so, the term f-the speed 1.

rc to th d ncins st in u c e o ve om 3 in Q of thelglassf as used in the albove description, is deemed to be the,peripheral speedof the roller required to drive. the glass with the necessary torque In the invention; either .a weight or a spring is used to drive the rollers andin all forms; oithe invention la spring can be'substituted tor a weight and yice-versa, Therefore in order to simplify the language of the claims, the term torque device? will be used to denoteaweight of spring applied sodas to exercise torque, ,and, x phrases such] as .to wind up the torquedevice,

will be u sedvto denote either to raise theweight;

or to extender compress a spring which operates by reason of its extension or compression respectively Having described our invention, we declare that what we claim and desire to secure by Letters Patent isz 1. In a glass finishingapparatus of the type in which a continuous strip of glass is advanced to andthrough the apparatus from a lehr entrained with a continuous strip forming-machine and in which the speed of advance of the continuous overcome the frictional, resistance between the strip andthe finishing tools the rollers of each pair contacting with the oppositesides of the advancing strip, a torque device applied to at least one rollerof each pair to exercise a substantially constant torque thereon, and motor driven means adapted to Wind up the torque device, the speed of the motor drivenmeans corresponding at intervals, to a peripheral roller speed which is higher thanthe speed at which the strip is advanced.

2. In a glass finishing apparatus of the type in which a continuous strip of glass is advanced to and through the apparatus from a lehr entrained witha continuous strip forming machine and in which the speed of advance of the continuous strip through the finishing apparatus is determined" by the speed of formation of the strip,

the combination of a plurality of pairs of stripgripping rollerslocated at intervals along-the length of the finishing apparatus for applyinga tractive force to the advancing strip sufi'icient to overcome the frictional resistance between the stripand the finishing tools, the rollers of each pair contacting with the opposite sides of the adv vancing strip, a torque device applied to at least,

one1 roller of each pair to exercise a substantially constant torquethereon through a chain, and

motor driven means operating on the said chain adapted to wind up the torque device, the speed of the motor driven means corresponding at intervals to a peripheral roller speed vwhich is higher than the speed at which the strip is advanced.

3. In a glass finishing apparatus of the type in which a continuous strip of glass is advanced to and through the apparatus from a lehr entrained with a continuous strip forming machine and in which the speed of advance of the continuous strip through the finishing apparatus is determined by the speed of formation of the strip, the combination of a plurality of pairs of strip-gripping rollers located at intervals along the length the-Irictionalresistance between the strip. and

the finishing too1s,-\-the rollers of each paincon tacting with the opposite sides; of the advancin :1 ,1 strip a torque device applied to at least one, roller; of each -pair to exercise 3 a substantially. constant torque theronthrough a gear wheel; adapted to ,rotate on its own; axis and, as ,they; torque device is wound or unwinds to move bodily; and motor. driven-1 ,means engaging the said 1 ear wheel and adaptedto wind up the-torque 1 device,;;the speed of the motor driven vmeans cor-,

responding at intervals to a peripheral roller speed which is higher than the speed at which" the strip is advanced. 4. In a glass; finishing apparatus o the type in which a continuous strip of glassis advanced to andthrough-the apparatus iro-rn a lehr entrained with a continuous stripforming machine and in which the speed of advanceof the contin- ,1

uous strip through the finishingapparatus is de:

termined by the-speedpf formation of the strip; the combination of a plurality of pairs of strip- 1 gripping rollers located at intervals along \the length of the finishing apparatus for applyinga tractive force; to the advancing strip sufficient to overcome theirictional resistancebetween the strip andthe finishing tools, .the rollers of each pair contacting with the opposite sides of the advancing-strip, a torque device appliedto at least oneroller pf each pair to exercise asubstantially constant torque thereon, motor driven 1 meanszactingcontinuously to tend to wind up 3 i the torquedevice, andmeans, dependent on the ex lfint to whichthe torque device is woundup,

for varyingthespeed of the motor driven means from a speed corresponding to a peripheral roller speed which is higher than thespeed .at which the strip is advanced to one which is lower thanv the said strip speed, and vice versa.

5. In a glass finishingapparatus of the type in which a continuous strip of glass is advanced to and through the apparatus from a lehr entrained with a continuous strip formingmachine and in which the speed of advance of thecontinuous strip throughethe. finishingwapparatus is deter,- mined by the speed of formation of the strip, the combinationof a plurality of pairs of stripgripping rollers located at intervalsalong. the length of the ifinishing apparatus for applying atractive force .to the advancing strip suflicient to overcome the irictional resistance between the stripandlthe finishing tools, the rollers of each pair. contacting with the opposite-sides of the advancing strip, a torquendevice applied to at leastone roller of each pair to exercise a sub-1;.

stantially, constant torque thereon, and motor driven meansgacting intermittently to wind up the torque devicewhen the torque device is unwound to a predetermined extent, the speed of the motor; driven means corresponding to a pe-;

ripheral rollerspeed which'is higher; than the speed,a t which thestrip is advanced.

6. In a glass; finishing apparatus of the type in which a continuous strip of glass is advanced to to overcome the frictional resistance between the strip and the finishing tools, the rollers of each pair contacting with the opposite sides of the advancing strip, a torque device applied to at least one roller of each pair to exercise a substantially constant torque thereon, motor driven means comprising a shaft adapted to drive means for winding up the torque devices of a plurality of pairs of rollers, gearing comprising a clutch between the said shaft and the means for winding up each individual torque device, and means for engaging the clutch when the torque device is unwound to a predetermined extent, the speed of the said shaft corresponding to a peripheral roller speed which is higher than the speed at which the strip is advanced.

'7. In a glass finishing apparatus of the type in which a continuous strip of glass is advanced to and through the apparatus from a lehr entrained with a continuous strip forming machine and in which the speed of advance of the continuous strip through the finishing apparatus is determined by the speed of formation of the strip, the combination of a plurality of pairs of strip-gripping rollers located at intervals along the length of the finishing apparatus for applying a tractive force to the advancing strip sufficient to overcome the frictional resistance between the strip and the finishing tools, the rollers of each pair contacting with the opposite r sides of the advancing strip, a torque device applied to at least one roller of each pair to exercise a substantially constant torque thereon, a variable speed motor operating continuously to tend to wind up the torque device, and means actuated when the torque device is nearly fully unwound for increasing the motor speed to a speed sufiicient to wind up the torque device and, when the torque device is nearly fully wound up, for diminishing the motor speed to a speed which allows the torque device to unwind.

8. In a glass finishing apparatus of the type in which a continuous strip of glass is advanced to and through the apparatus from a lehr entrained with a continuous strip forming machine and in which the speed of advance of the continuous strip through the finishing apparatus is determined by the speed of formation of the strip, the combination of a plurality of pairs of strip-gripping rollers located at intervals along the length of the finishing apparatus for applying a tractive force to the advancing strip sufficient to overcome the frictional resistance between the strip and the finishing tools, the rollers of each pair contacting with the opposite sides of the advancing strip, a torque device applied to at least one roller of each pair to exercise a substantially constant torque thereon, a shaft adapted to drive means for winding up the torque devices of a plurality of pairs of rollers, two sets of gearing, each comprising a clutch, between the shaft and each individual torque device, one set adapted to turn the means tending to wind up the torque device at a speed sulficient to wind it up and the other set adapted to turn it at a lower speed which allows the torque device to unwind, and means for engaging the clutch in the former set of gearing and disengaging the other clutch when the torque device is nearly fully unwound, and for engaging the clutch in the latter set of gearing and disengaging the other clutch when the torque device is nearly fully wound up.

9. In a glass finishing apparatus of the type in which a continuous strip of glass is advanced to and through the apparatus from a lehr entrained with a continuous strip forming machine and in which the speed of advance of the continuous strip through the finishing apparatus is determined by the speed of formation of the strip, the combination of a plurality of pairs of strip-gripping rollers located at intervals along the length of the finishing apparatus for applying a tractive force to the advancing strip sulficient to overcome the frictional resistance between the strip and the finishing tools, the rollers of each pair contacting with the opposite sides of the advancing strip, and one roller of each pair being made of a material which can slip on the strip more readily than the other roller, a torque device applied to each pair of rollers to exercise a substantially constant torque thereon, and motor driven means adapted to wind up the torque device, the speed of the motor driven means corresponding at intervals to a peripheral roller speed which is higher than the speed at which the strip is advanced.

10. In a glass finishing apparatus of the type in which a continuous strip of glass is advanced to and through the apparatus at a speed determined solely by its advancing means, the combination of a plurality of strip-gripping rollers located at intervals along the length of the finishing apparatus for applying a tractive force to the advancing strip sufficient to overcome the frictional resistance between the strip and the finishing tools, the rollers of each pair contacting with the opposite sides of the advancing strip, and driving means, one for at least one of each pair of said strip-gripping rollers, each of said driving means including torque devices operating automatically to exercise a substantially constant torque on at least one of the rollers of each pair. 11. In a glass finishing apparatus of the type in which a continuous strip of glass is advanced to and through the apparatus at a speed determined solely by its advancing means, the combination of pairs of continuously-acting members for applying a tractive force to the advancing strip sufiicient to overcome the frictional resistance between the strip and the finishing tools, and driving connections for at least one member of each pair of said continuously-acting members, each of said connections including a torque device operating automatically to apply through said continuously-acting means a substantially constant tractive force to the advancing strip.

GRANVILLE HUGH BAILLIE. FREDERIC BARNES WALDRON. 

